PT100 - PT1000 Setup

Resistance thermometers, also called resistance temperature detectors (RTDs), are sensors used to measure temperature. RTDs, which have higher accuracy and repeatability, allow for higher temperature print materials (up to 600C in some cases) and can be a very useful upgrade to your Jubilee build. The most commonly used RTDs in 3D printers are the PT100 and PT1000 series sensors, which require a little setup to work properly with a Duet controller. PT1000 sensors have only recently become more available to use, and are somewhat easier to configure since they can plug directly into your Duet controller board. PT100 sensors need an extra daughterboard to condition the signal and make it something readable by the microprocessor.

For a good comparison of the virtues of the common Temperature Sensors see the Duet Wiki page on Temperature_sensors. For additional information, please refer to the Duet3D wiki page for setting up RTDs.

A note on wiring issues and behavior

RTD's (aka PT100/PT1000) are positive resistance temperature devices meaning that their resistance increases with higher temperature readings, which is the exact opposite behavior of a what typical 3D printer NTC thermistor would do! This means that if you read a high resistance value on your thermistor channel/wires, you are interpreting a reading for a high temperature, and a low temperature would read as a short or low resistance measured across the thermistor.

Also note that the Duet Meastro and Duet 3HC boards have thermistor inputs with a 2.2k ohm sense resistor, which means they are optimised to function with PT1000's much better than a Duet WiFi/Ethernet board (which have 4.7k ohm sense resistors on board). This value if not specified in the M308 lines will be automatically selected by the FW For the board in use. It is only listed for completeness.

PT100 Setup

To be able to use PT100 sensors on a Duet controller board, you will need to also install a PT100 daughter board to be able to accurately measure the signal from the RTD for the Duet controller.

RepRapFirmware 3.x

The following is a sample working setup using 2 PT100's on a Duet Wifi board running RRF3.1.1.

Always note your maximum temperature limits, your channel mapping to RTDs and heaters, and your pin names.

; Heaters
M143 S300 ; Set maximum heater temperature to 300C
M308 S0 P"spi.cs2" Y"rtd-max31865" F50
M308 S1 P"spi.cs1" Y"rtd-max31865" F50
M950 H0 C"bedheat" T0
M950 H1 C"e0heat" T1
M140 H0                                 ; map heated bed to heater 0

RepRapFirmware 2.x and 1.x

The following is a sample working setup using 2 PT100's on a Duet Wifi board running RRF2.0.5.

Always note your maximum temperature limits, your channel mapping to RTDs and heaters, and your pin names.

; Heaters
M305 P0 X201 ; Set thermistor + ADC parameters for heater 0 and remap it to channel 201
M305 P1 X200 ; Set thermistor + ADC parameters for heater 1 and remap it to channel 200

PT1000 Setup

PT1000 sensors can be directly plugged into a Duet controller board without any additional hardware or electronics.

RepRapFirmware 3.x

This is a working setup for 2 PT1000 sensors connected to the first 2 Thermistor inputs on a Duet3 running RRF3.1.1

; Heaters
M308 S0 P"temp0" Y"pt1000"                    ; configure sensor 0 as PT1000 on pin temp0
M950 H0 C"out0" T0                            ; create bed heater output on out0 and map it to sensor 0
M143 H0 S120                                  ; set temperature limit for heater 0 to 120C
M307 H0 B0 S1.00                              ; disable bang-bang mode for the bed heater and set PWM limit
M140 H0                                       ; map heated bed to heater 0
M308 S1 P"temp1" Y"pt1000"                    ; configure sensor 1 as PT1000 on pin temp1
M950 H1 C"out1" T1                            ; create nozzle heater output on out1 and map it to sensor 1
M143 H1 S280                                  ; set temperature limit for heater 1 to 280C
M307 H1 B0 S1.00                              ; disable bang-bang mode for heater  and set PWM limit

You may want to adjust the M143 line for your own usage case and the same will go for the input and output pins.

RepRapFirmware 2.x and 1.x

(TBA)'

Further precautions

DO NOT FORGET TO PID TUNE THE SYSTEM EVERY TIME YOU MAKE A CHANGE TO IT